A metal-free formylation of imidazopyridines with K2S2O8 via direct decarboxylative cross-coupling of glyoxylic acid is described. This reaction features broad substrate scope, good functional group tolerance, and generate products in good yields. The involvement of radicals in the course of the reaction has been demonstrated by radical trapping experiments with 2,2,6,6-tetramethylpiperidine-1-oxyl and 2,6-di-tert-butyl-4-methylphenol (BHT).

Asymmetric Olefin Metathesis (AOM) represents a highly versatile synthetic tool to lead to relevant chiral building blocks with excellent enantiopurity. As the Z-alkene moiety is ubiquitous in a wide range of natural products, the development of catalysts which are able to control both the Z-selectivity and the enantioselectivity of metathesis transformations is in high demands. This review aims to provide a comprehensive overview covering all the breakthroughs accomplished in the field of challenging Z-enantioselective olefin metathesis, which is of interest in the total synthesis of complex molecules.

(R)-Pantolactone, an intermediate in the syntheses of Vitamin B5 and coenzyme A, is an important chiral molecule often used as a food additive, chiral auxiliary, and chiral starting material for organic transformations. Enantioenriched pantolactones are predominantly produced by biological fermentation and chemical synthesis approaches. Herein, we present a review of recent developments in the asymmetric synthesis of pantolactone via different methods, and systematically summarize the characteristics and advantageous features of these strategies. Among the strategies discussed herein, the direct asymmetric catalysis of glyoxylate and isobutyraldehyde with small organocatalyst molecules has attracted growing attention owing to its good step-economy, commercially available starting materials, absence of toxic reagents, mild reaction conditions, convenient operation, and low catalyst loading. These characteristics render the direct asymmetric route to pantolactone a particularly attractive procedure. This review provides valuable guidance for the design and synthesis of enantioenriched pantolactone and its analogs.

An efficient rhodium(III)-catalyzed C−H bond activation/allylation reaction of 3-aryl-1H-indazoles with easily available vinylethylene carbonate has been reported. A series of allyl alcohol substituted 3-aryl-1H-indazoles were obtained.

Abstract

An efficient rhodium(III)-catalysed C−H activation of 3-aryl-1-H-indazoles with easily available vinylethylene carbonate has been reported. A series of allyl alcohol substituted 3-aryl-1-H-indazoles were obtained with broad functional groups tolerance and favourable stereoselectivity. Notably, C−H and C−O bonds were selectively activated in “one pot” manner, releasing CO₂ as the sole by-product and avoiding external oxidant. This protocol provides a powerful approach for the post stage C−H allylation of indazole-based substrates.

Here, we reported novel three-dimensional scaffolds in one molecule to achieve DSE. These molecules allowing for rapid access showed completely different molecular packing manners from those of planar conjugated molecules and exhibited excellent optoelectronic properties with diminished intermolecular π−π stacking interactions due to steric hindrance.

Abstract

Organic fluorophores with highly efficient luminescence in both solution and solid states have attracted significant attention due to their ability to circumvent the limitations of aggregation-caused quenching and aggregation-induced emission type molecules. However, their development and wide-range applications are hampered by extremely complex synthetic methodologies and limited frameworks with dual-state emission (DSE) structural characteristics. In sharp contrast to the reported luminogens with big and planar π systems or highly conjugated and twisted structures, we discovered novel three-dimensional scaffolds in one molecule to achieve DSE. These molecules allowing for rapid access showed completely different molecular packing manners from those of planar conjugated molecules and exhibited excellent optoelectronic properties with diminished intermolecular π−π stacking interactions due to steric hindrance. Our findings should open new avenues for designing DSE molecules with new frameworks, which will enable more successful development of dual-state emitters for their broad applications in the future.

A practical methodology for the synthesis of triacylglycerides utilizing fatty acids activated by 1,1’-carbonyldiimidazole (CDI) was developed to obtain protiated and deuterated medium chain triglyceride (MCT) oils as well as a synthetic plant oil mimic. New insights into the mechanism of the CDI activation were gained using deuterated substrates and via density-functional theory (DFT) calculations.

Abstract

Synthetic model triacylglyceride oils are important compounds for applications in pharmaceutical and food chemistry. Herein, a practical and highly efficient methodology for the synthesis of saturated and unsaturated triacylglycerides utilizing saturated and unsaturated fatty acids activated by 1,1’-carbonyldiimidazole (CDI) has been developed and applied in the synthesis of deuterated medium chain triglyceride (MCT) oil for studies of plant-based and diary food emulsions. The deuterium labelled compounds were used to gain new insight into the mechanism of the reaction, which was confirmed by density-functional theory (DFT) calculations.

The hydrohalogenation of olefins is one of the most straightforward methods to access alkyl halides. Despite safety hazards, using pure hydrogen halide gas remains the most atom economic way of performing hydrohalogenation reactions. In this work, we describe the solvent-free hydro- and deuteriohalogenation of olefins using down to near-stoichiometric amounts of hydrogen and deuterium halide gas. Two-chamber reactors are employed as an enabling platform to access these reactive gases in a laboratory setting. Ex situ generation from inexpensive and readily available precursors provides on-demand access to these gases (hydrogen chloride, deuterium chloride, hydrogen bromide, deuterium bromide, hydrogen iodide, and deuterium iodide) with precise stoichiometric control. Upon chemo- and regioselective conversion of the substrate, the halide products may be isolated without the need for any work-up or purification steps making it a clean and labor-, waste- and cost-effective method.

Ribosyl adenosine 5′,5″-diphosphate is a poly(ADP-ribose) fragment covalently bonded to a protein during post-translational modification. Poly(ADP-ribose) is involved in several biological processes such as DNA repair and cancerization. Herein, we report the development of two synthetic approaches to the poly(ADP-ribose) fragment via a common precursor. The major difficulty in the synthesis of the fragment is the α-(1″→2′)-glycosidic bond formation between the ribose and adenosine because of the lack of neighboring group participation and low reactivity of the 2′-hydroxyl group. The first approach employed an indirect method that involved stepwise assembly of the ribosyl adenosine framework by O-ribofuranosylation of a commercially available ribose acceptor and subsequent N-glycosylation of N6-benzoyl adenine (11 linear longest sequence (LLS) steps, 14.5% overall yield). In the second approach, the direct O-ribofuranosylation of a known 6-chloropurine riboside acceptor was adopted (9 LLS steps, 10.3% overall yield). Thus, two practical synthetic approaches to the target fragment were successfully established in terms of the number of LLS steps and overall yield. Furthermore, the precursor was converted into a conjugation-ready building block, primed for application in ADP-ribose oligomer synthesis.

Porphyrins that bear halogens at the meso-aryl positions are useful building blocks for the preparation of light-harvesting arrays and materials through cross-coupling procedures. Despite the wide use of such intermediates, their scale-up and purification are usually hampered by tedious chromatographic separations because of the statistical nature of the synthetic protocol and the similar polarity of the different products. Here, we propose the use of porphyrins bearing a triflatophenyl group as alternative starting materials for palladium cross-coupling reactions. In particular, purification of the zinc 5,10,15-triaryl-20-(4-triflatophenyl)porphyrin (ZnP-OTf) model compound by column chromatography proved to be much easier compared to porphyrin analogues that carry halogen substituents. This is the result of the increased polarity of compounds functionalized by highly polar triflate groups if compared to those substituted by halogens. To show the value of the triflatophenylporphyrin model compound in cross-coupling reactions, we developed a microwave-assisted Sonogashira protocol that quantitatively converts the ZnP-OTf to the corresponding alkynylphenylporphyrin, in relatively short reaction times. Finally, we showed that the proposed ZnP-OTf building block can be conveniently converted into an alkynyl-linked molecular wire to bridge the zinc porphyrin donor with the [60]fullerene acceptor in a molecular dyad.

A new strategy is reported for the C-H/C-H functionalization of 7-azaindazoles at the C6 position via a regioselective oxidative arylation using N-oxide activation. This methodology allowed selective and original access to C6-arylated 7-azaindazoles with different substituted arenes and heteroarenes.